Tripping devices

ABSTRACT

A high sensitivity and high-fidelity tripping device, comprises a magnetic circuit of U-shape with a coil on one of the legs of the U and a permanent magnet housed in the U adjacent the second leg of the U such that one pole lies against the base of the U. A plate of nonmagnetic material is secured to the second leg of the U, and an armature is normally held magnetically on the two legs of the U and is releasable under spring action by rocking on the second leg of the U between two projections of the plate. The polar face of the second leg of the U is cut into two sections by a wide, central channel, which reduces it to two narrow, separated teeth, and the polar face of the first leg of the U is reduced to a narrow tooth between two shoulders; a regulating screw of magnetic material is screwed into the base of the U, parallel to the legs of the U, between the coil and the permanent magnet; and a flux collector, of magnetic material has a flat part located through the intermediary of a plate of nonmagnetic material on the free end of the permanent magnet and is arrested at a short distance from the second leg of the U and also has a part turned upwards towards the armature and arrested at a short distance from the armature.

United States Patent [72] Inventor Paul A. G. Canonne Chelles, France [21] App1.No. 875,214 [22] Filed Nov. 7, 1969 [45] Patented Oct. 19, 1971 [73] Assignee L'lndustrie Electrique De La Seine Seine-Saint-Denis, France [32] Priority Jan. 6, 1969 [33] France [31] 6900052 [54] TRIPPING DEVICES 17 Claims, 9 Drawing Figs.

[52] US. Cl. 335/229, 335/ 1 79 [51] Int. Cl. H0lf7/08 [50] Field of Search 335/229, 230,179,l80,181,182, 78, 79, 80, 81, 82, 83, 84, 85, 86

[56] References Cited UNITED STATES PATENTS 1,743,494 1/1930 Snyder 335/86 2,580,123 12/1951 Pfleger 335/181 2,991,395 7/1961 Allen et al, 335/229 3,161,806 12/1964 Gordon, Jr. 335/230 3,317,871 5/1967 Adams 335/230 Primary Examinerl lar0ld Broome Attorney-Waters, Roditi, Schwartz & Nissen ABSTRACT: A high sensitivity and high-fidelity tripping device, comprises a magnetic circuit of U-shape with a coil on one of the legs of the U and a permanent magnet housed in the U adjacent the second leg of the U such that one pole lies against the base of the U. A plate of nonmagnetic material is secured to the second leg of the U, and an armature is normally held magnetically on the two legs of the U and is releasable under spring action by rocking on the second leg of the U between two projections of the plate. The polar face of the second leg of the U is cut into two sections by a wide, central channel, which reduces it to two narrow, separated teeth, and the polar face of the first leg of the U is reduced to a narrow tooth between two shoulders; a regulating screw of magnetic material is screwed into the base of the U, parallel to the legs of the U, between the coil and the permanent magnet; and a flux collector, of magnetic material has a flat part located through the intermediary of a plate of nonmagnetic material on the free end of the permanent magnet and is arrested at a short distance from the second leg of the U and also has a part turned upwards towards the armature and arrested at a short distance from the armature.

PATENTEDnm 19 I97! SHEET 1 OF 2 FIGQ nurrmc DEVICES The invention relates to a high sensitivity and high fidelity electromagnetic tripping device.

Such tripping devices are currently used in electrical applications, not only for the protection of large electrical installations, but also for the protection of domestic electrical appliances, and thus at one and the same time for the protection of apparatus and for the protection of humans.

Such tripping devices are known, the structure of which comprises a fixed magnetic circuit (stator) with a permanent magnet and a coil, and a movable armature closing the said magnetic circuit in the normal position, a spring acting on the armature to urge it to a released position. The stator is generally U-shaped, the coil surrounding one of the legs of the U, and the permanent magnet being housed inside the U, against the second leg of the U with a pole against the base of the U. In such a tripping device, in the normal position, the armature is attracted magnetically against the two polar sides of the legs of the U by a part of the magnetic flux from the permanent magnet cooperating with the magnetic circuit, the other part of this flux-generally the major part-being shunted by a part, of suitable reluctance, of the said magnetic circuit. The release of the movable armature is achieved by the decrease of fiux circulating in the movable armature, by sending a current of suitable direction in the coil. Thus the movable armature reacts to the action of its spring and rocks on an edge of the second leg of the U thus producing the desired mechanical efi'ect (for example operation of contacts or operation of a circuit breaker).

' Hitherto, such a tripping device had the disadvantage of lacking reliability, for example the air gaps between the armature and the two polar faces of the legs of the U varying in service in a hazardous manner, and/or become fouled by magnetic dust which adheres to them.

One object of the invention is to provide a high-fidelity tripping device in which the aforesaid disadvantage is obviated or mitigated by a plurality of first means as hereinafter defined.

The aforesaid tripping device has also had the disadvantage that, even with mass production, the release point of the armature varies in an irregular manner from one tripping device to another.

A further object of the invention is to provide a tripping device in which the aforesaid disadvantage is obviated or mitigated, by second means as hereinafter defined independently of the said first means.

Until now, such a tripping device also had the disadvantage of being particularly sensitive to temperature, which greatly changes its release point.

A still further object of the invention is to provide a tripping device in which the aforesaid disadvantage is obviated or mitigated by a third means as hereinafter defined, independently of the said first means and cooperating with the said second means.

Finally another object of the present invention is to provide a tripping device with its sensitivity notably increased by the said third means and used according to another manner.

Briefly, the said first means according to the invention relate to the airgaps between the armature and the two polar faces of the legs of the U; the polar face of the second leg of the U (i.e. on which the armature rocks during release) is divided into two sections by a large central slot, which reduces it to two separated, narrow teeth; the polar face of the other leg of the U (ie the one supporting the coil) being reduced to one narrow tooth between two shoulders.

Thus, the present invention replaces the supporting of the armature on two surfaces by its support on three teeth, which is a mechanical improvement which reduces fouling. On the one hand, it is easier to adjust three teeth than two surfaces and the support on three teeth approaches an ideal support on three points, and, on the other hand, the magnetic dust will lodge in the slots on the edges of which it is attracted. Finally the rocking of the armature during release no longer takes place over the relatively long edge of the leg of the U, but on two short, relatively remote sections of this edge and this arrangement ensures a particularly stable rocking, and avoids the necessity of adjusting the said edge. In addition, the said first means according to the invention relates to the surface condition of the parts fonning the airgap: on the one hand, the armature receives polished surfacing, and on the other hand, the teeth of the legs of the U are grooved, then are given a matt finish by cold-hammering; the said finishing operation increases the uniformity of the airgaps, and the magnetic dust lodges in the hollows of the grooves.

Briefly, the said second means according to the invention is a regulating screw, of magnetic material, screwing into the base of the U parallel to the legs of the U between the coil and the permanent magnet, this second means cooperating, preferably but not necessarily with the third means, and the advantages of the combination being described below.

Briefly, the said third means according to the invention is a flux collector, of magnetic material, comprising a flat part, located through the intermediary of a small plate of nonmagnetic material on the free end of the permanent magnet and terminating at a short distance from the leg of the U, and a part turned up towards the armature but terminating at a short distance therefrom.

This flux collector affords an additional path to the useful flux going from the permanent magnet to the armature, which makes it possible either to increase the force keeping the armature in position, or to obtain the same force keeping the armature in position by means of a permanent magnet furnishing less flux. Moreover and due to this very fact, the flux density in the second leg of the U decreases, and thus its reluctance decreases. This results in an increase in the sensitivity of the tripping device. The end of the said regulating screw is below the said flux collector and more or less in its vicinity, and diverts to a greater or lesser degree the flux passing through the collector, and thus makes possible the regulation of the sensitivity of the tripping device.

Finally the invention provides that the magnetic material constituting the said flux collector is chosen in such a manner as to regulate to any desired value, the thermal characteristic of the tripping device. For example the thermal characteristic of other parts of the tripping device can be compensated for, which makes the release of the armature independent of temperature, or on the contrary a thermal characteristic of the tripping device can be obtained which compensates for a thermal characteristic of another device, such as its toroidal feed transformer.

A preferred embodiment of tripping device incorporating the various aspects of the invention will now be described by way of example only with reference to the accompanying drawings in which:

FIG. 1 shows a perspective view of the assembled stator of a tripping device in accordance with the invention;

FIG. 2 is a perspective view of the plate of the stator shown in FIG. 1;

FIG. 3 is a perspective view of the magnetic U illustrating the first aspect of the invention;

FIGS. 4 and 5 show respectively in section and in plan, the magnetic U and illustrate the second aspect of the invention;

FIG. 6 is a perspective view of part of the magnetic U, and illustrates the third aspect of the invention;

FIG. 7 is a diagrammatic section showing the magnetic cooperation of the different parts of the tripping device;

HO. 8 is a circuit diagram for the device shown in FIG. 7; and

FIG. 9 is an explanatory graphical illustration.

With reference to FIGS. 1 and 2 the stator comprises, in a manner known per se, a stationary, magnetic circuit in the Shape of a U, with a base 1 and legs 2 and 3. An electric coil 4 surrounds the leg 3 and a permanent magnet 5 is housed inside the U, against the leg 2, with one pole thereof against the base 1. A plate 6, of nonmagnetic material, for example of nylon, covers the leg 2 and, by means of a flange 7, retains the coil 4.

The plate 6 is provided with two rounded projections 8 between which an armature (not shown in the drawing) pivots. The aspects according to the invention will be described hereafter in succession.

With reference to FIG. 3, which is a perspective view of the magnetic U, the leg 2 of the magnetic U according to the invention ends in two narrow, spaced teeth 11, separated by a wide central channel 12, and disposed between two shoulders 13 cooperating with cutout parts 14 of the plate 6. The leg 2 is provided with a window 15 in which there is secured a nose 17 of the plate 6. The base 1 of the U is provided with two bosses 18 on which the permanent magnet rests and with a threaded hole 19 for a regulating screw to be described later. Preferably, but not necessarily, the base 1 of the U is provided with a lateral cutout 21, as shown, modifying its magnetic reluctance as desired or expedient. The leg 3, already of greatly reduced width in order to pass into the coil 4, terminates in a narrow tooth 22 between two shoulders 23. Thus, according to the invention, the armature is supported by the three teeth 11 and 22, with the previously noted advantages. Preferably, but not necessarily, the surface of each of the two teeth 11 of the leg 2 can be equal in area to half the surface area of the tooth 22 of the leg 3. The armature is made into as perfect a plane surface as possible, and its surface condition is equivalent to a brilliant polish; the surfaces of the three teeth 1 l and 22 are trued, grooved, then given a matt finish by coldhammering.

With reference to FIGS. 4 and 5, which show, in section and in plan view, the magnetic U and certain of its associated parts, the threaded hole 19 of the base 1 of the U receives a regulating screw 25, extending upwardly between the permanent magnet 5 and the coil 4, for example to about the same height as the permanent magnet. Preferably, but not necessarily, the regulating screw 25 is restrained by an edge 26 of a lower cheek of the coil 4. The cheek is made, for example of thermoplastic material, which ensures that the screw 25 is retained in the regulating position to which it has been adjusted. The regulating screw 25 is made of magnetic material, for example soft iron and its function, from the magnetic point of view, is to divert to itself a greater or lesser part of the magnetic flux sent by the permanent magnet to the armature. The invention proposes to enhance the efficiency of the regulating screw by positioning it more or less in the vicinity of the permanent magnet, without however bringing it into contact with the latter, as well as by the choice of the dimensions and material of this regulating screw. In addition this regulating screw may, preferably, but not necessarily, cooperate with the flux collector as described hereafter.

With reference to FIG. 6, which is a partial perspective view of the magnetic U, there is placed on the top of the permanent magnet 5, a small plate 31 of nonmagnetic material, with a flange 32 lying along the leg 2. On this plate 31 there is arranged a flux collector 33, of magnetic material, comprising a flat part or plate 41, a free edge 42 at one end of which abuts the flange 32 of the plate 31, and having at the other end thereof a part 43 which extends upwardly but does not reach the armature. Preferably, but not necessarily, the free edge 42 above the permanent magnet comprises a central slot 44 between two projections or teeth 45. The plate 31 and collector 33 are retained in position by the plate 6 and its two lateral extensions 36 and 37, and by an edge 46 of the upper check of the coil 4 (FIG. 1). The role of this flux collector is to cause a part of the magnetic flux sent by the permanent magnet towards the armature to pass through itself, thus reducing the flux in the leg 2, the reluctance of which decreases as already described: during tripping, the reversed flux necessary can consequently be furnished by a smaller number of ampereturns at the coil 4, which increases the sensitivity of the tripping device, and this although the magnetic attraction of the armature has been increased considerably. The shape of this flux collector is fixed: on the one hand, its plate 41, which has a polar function, determines the magnitude of flux channeled through the said additional route; on the other hand, the

height of its bent part 43 determines the reluctance of the said additional route.

There will now be described, in a more detailed manner, the magnetic cooperation of the different parts described above. With reference to FIG. 7 which is a diagrammatic section, in which the components described above are designated by the same reference numerals, the permanent magnet 5 is shown with its two polar faces N and S (which could naturally be reversed) and an armature 38 is shown in contact with the U, which is its normal position, despite the action of its retractor spring 39. The total flux of the permanent magnet 5 is divided into: a flux D1, which closes again directly through the leg 2 of reluctance R1; a flux D2, which passes through the leg 2 and the armature 38 (reluctance R2) to the right of the bent part 43 of the flux collector 33, where it joins a flux b3 having passed through this collector (reluctance R3), these two fluxes then passing together through the armature 38, the leg 3 and the base 1 (reluctance R23), and finally a flux b4 passing through the regulating screw 25 (reluctance R4). Only this last reluctance R4 can be regulated (through the screw 25): given that it is placed in shunt on the source of flux 5 (FIG. 8) and that the reluctance R1 is much weaker than the others, its regulation varies in reverse linear relationship to the sum of the fluxes b2-Hb3) which are the fluxes keeping the armature 38 in place; the screwing of the screw 25 reduces the reluctance R4, thus increases the flux b4, thus decreases the sum of the two fluxes l 2+3). The flux collector 33, which determines toe flux b3 by the reluctance R3, has an effect dependent upon the value of this flux 2 3, the temperature and the quality of the material of which it is made. It will be noted that, according to the invention, the regulations of the fluxes D3 and D4 are thus assured by two independent members, namely the flux collector 33 (at manufacture) and the regulating screw 25 (by adjustment).

What we claim is:

l. A high sensitivity and high-fidelity electromagnetic tripping device, comprising a magnetic circuit of U-shape a coil of one of the legs of the U, a permanent magnet housed in the U adjacent the other leg of the U with one pole thereof adjacent the base of the U, a plate of nonmagnetic material secured to said other leg of the U, and an armature normally held magnetically on the two legs of the U and releasable by rocking on the second leg of the U between the two projections of the plate under the action of a spring, the free end face of the said second leg of the U being formed with a wide cen tral channel defining two spaced narrow projections and the free end face of the said first leg of the U being for-med with a narrow tooth defining two spaced shoulders.

2. A tripping device according to claim 1, wherein the armature has a highly polished surface finish and the surface of the said teeth has a matt finish.

3. A tripping device according to claim 1, wherein the surface of each of the two teeth of the second leg is about equal in area to half the surface area of the tooth of the first leg.

4. A tripping device according to claim 1, wherein the base of the U is provided with two bosses on which the permanent magnet seats and with a lateral cutout increasing its reluctance.

5. A tripping device according to claim 1, comprising a regulating screw, of magnetic material screwed into the base of the U, parallel to the legs of the U, between the coil and the permanent magnet.

6. A tripping device according to claim 5, wherein the said screw is restrained by the edge of a cheek of the coil.

7. A tripping device according to claim 1, comprising a flux collector, of magnetic material including a flat part, located through the intermediary of a plate of nonmagnetic material on the free end of the permanent magnet and terminating at a short distance from the second leg, and a part turned upwards towards the armature and arrested at a short distance therefrom.

8. A tripping device according to claim 7, wherein the said flat part of the said flux collector, adjacent the side of the second leg of the U, ends in two teeth separated by a slot.

9. A tripping device according to claim 7, wherein the plate is provided with two projections retaining the collector and the plate and the collector is retained by the upper cheek of the said coil.

10. A high sensitivity and high-fidelity electromagnetic tripping device, comprising a magnetic circuit of U-shape, a coil on one of the legs of the U, a permanent magnet housed in the U, adjacent the second leg of the U, with one pole thereof adjacent the base of the U, a plate of nonmagnetic material secured to the second leg of U, an armature normally held magnetically on the two legs of the U and releasable by rocking on the second leg of the U between two projections of the plate under the action of a spring and a regulating screw of magnetic material screwed into the base of the U, parallel to the legs of the U, between the coil and the permanent magnet.

11. A tripping device according to claim 10, wherein the said screw is restrained by the edge of a cheek of the coil.

12. A tripping device according to claim 10, comprising a flux collector, of magnetic material, including a flat part located through the intermediary of a second plate of nonmagnetic material on the free end of the permanent magnet and terminating at a short distance from the second leg of the U, and a part turned upwardly towards the armature and terminating at a short distance therefrom.

13. A tripping device according to claim 12, wherein the said flat part of the said flux collector on the side of the second leg of the U, ends in two teeth separated by a slot.

14. A tripping device according to claim 12, wherein the plate is provided with two projections retaining the collector and the second plate, and the collector is retained by the upper cheek of the said coil.

15. A high sensitivity and high-fidelity electromagnetic tripping device, comprising a magnetic circuit of U-shape, a coil on one of the legs of the U, a permanent magnet housed in the U adjacent the second leg of the U with one pole thereof adjacent the base of the U, a plate of nonmagnetic material secured to the second leg of the U, an armature normally held magnetically on the two legs of the U and releasable by rocking on the second leg of the U between two projections of the plate under the action of a spring, and a flux collector, of magnetic material having a flat part located, through the intermediary of a second plate of nonmagnetic material, on the free end of the permanent magnet and extending to within a short distance of the second leg of the U, and having a part bent upwardly towards the armature to within a short distance thereof.

16. A tripping device according to claim 15, wherein that end of the said flat part of the said flux collector adjacent the second leg of the U, is formed as two teeth separated by a channel.

17. A tripping device according to claim 15, wherein the plate is provided with two projections retaining the collector and the second plate, and the collector is retained by the upper check of the said coil. 

1. A high sensitivity and high-fidelity electromagnetic tripping device, comprising a magnetic circuit of U-shape a coil of one of the legs of the U, a permanent magnet housed in the U adjacent the other leg of the U with one pole thereof adjacent the base of the U, a plate of nonmagnetic material secured to said other leg of the U, and an armature normally held magnetically on the two legs of the U and releasable by rocking on the second leg of the U between the two projections of the plate under the action of a spring, the free end face of the said second leg of the U being formed with a wide central channel defining two spaced narrow projections and the free end face of the said first leg of the U being formed with a narrow tooth defining two spaced shoulders.
 2. A tripping device according to claim 1, wherein the armature has a highly polished surface finish and the surface of the said teeth has a matt finish.
 3. A tripping device according to claim 1, wherein the surface of each of the two teeth of the second leg is about equal in area to half the surface area of the tooth of the first leg.
 4. A tripping device according to claim 1, wherein the base of the U is provided with two bosses on which the permanent magnet seats and with a lateral cutout increasing its reluctance.
 5. A tripping device according to claim 1, comprising a regulating screw, of magnetic material screwed into the base of the U, parallel to the legs of the U, between the coil and the permanent magnet.
 6. A tripping device according to claim 5, wherein the said screw is restrained by the edge of a cheek of the coil.
 7. A tripping device according to claim 1, comprising a flux collector, of magnetic material including a flat part, located through the intermediary of a plate of nonmagnetic material on the free end of the permanent magnet and terminating at a short distance from the second leg, and a part turned upwards towards the armature and arrested at a short distance therefrom.
 8. A tripping device according to claim 7, wherein the said flat part of the said flux collector, adjacent the side of the second leg of the U, ends in two teeth separated by a slot.
 9. A tripping device according to claim 7, wherein the plate is provided with two projections retaining the collector and the plate and the collector is retained by the upper cheek of the said coil.
 10. A high sensitivity and high-fidelity electromagnetic tripping device, comprising a magnetic circuit of U-shape, a coil on one of the legs of the U, a permanent magnet housed in the U, adjacent the second leg of the U, with one pole thereof adjacent the base of the U, a plate of nonmagnetic material secured to the second leg of U, an armature normally held magnetically on the two legs of the U and releasable by rocking on the second leg of the U between two projections of the plate under the action of a spring and a regulating screw of magnetic material screwed into the base of the U, parallel to the legs of the U, between the coil and the permanent magnet.
 11. A tripping device according to claim 10, wherein the said screw is restrained by the edge of a cheek of the coil.
 12. A tripping device according to claim 10, comprising a flux collector, of magnetic material, including a flat part located through the intermediary of a second plate of nonmagnetic material on the free end of the permanent magnet and terminating at a short distance from the second leg of the U, and a part turned upwardly towards the armature and terminating at a short distance therefrom.
 13. A tripping device according to claim 12, wherein the said flat part of the said flux collector on the side of the second leg of the U, ends in two teeth separated by a slot.
 14. A tripping device according to claim 12, wherein the plate is provided with two projections retaining the collector and the second plate, and the collector is retained by the upper cheek of the said coil.
 15. A high sensitivity and high-fidelity electromagnetic tripping device, comprising a magnetic circuit of U-shape, a coil on one of the legs of the U, a permanent magnet housed in the U adjacent the second leg of the U with one pole thereof adjacent the base of the U, a plate of nonmagnetic material secured to the second leg of the U, an armature normally held magnetically on the two legs of the U and releasable by rocking on the second leg of the U between two projections of the plate under the action of a spring, and a flux collector, of magnetic material having a flat part located, through the intermediary of a second plate of nonmagnetic material, on the free end of the permanent magnet and extending to within a short distance of the second leg of the U, and having a part bent upwardly towards the armature to within a short distance thereof.
 16. A tripping device according to claim 15, wherein that end of the said flat part of the said flux collector adjacent the second leg of the U, is formed as two teeth separated by a channel.
 17. A tripping device according to claim 15, wherein the plate is provided with two projections retaining the collector and the second plate, and the collector is retained by the upper cheek of the said coil. 